The present invention relates to a vertical die casting machine, provided with a tilting device, in which machine a molten metal in a casting sleeve is injected by an injection plunger into a die formed by stationary and movable molds, and the molten metal is poured into the casting sleeve while the sleeve is spaced apart from the stationary mold.
One such machine is disclosed in U.S. Pat. No. 4,088,178 of which the inventors are the same as those of the present invention. In such a machine, the casting sleeve and the injection plunger are designed so that they can be moved relative to the stationary mold by different driving sources. This driving system is apt to raise a problem in that the positional relationship between the injection plunger and the casting sleeve is changed and thus the space for the molten metal in the sleeve, defined by the sleeve and plunger, is changed in the steps of: pouring the molten metal into the sleeve from above the sleeve; moving the sleeve and plunger with the molten metal toward the stationary mold; and of contacting the sleeve with the stationary mold. This change results in variations of the axial length of the space and thus of the liquid level of the molten metal in the sleeve. Accordingly, there is the disadvantageous possibility that the molten metal may be scattered and agitated. Furthermore, when the molten metal is moved considerably within the sleeve, it is inclined to be cooled and readily oxidized. In some cases, only the sleeve is moved upward and the plunger is disengaged from the sleeve, causing the disadvantageous possibility of dropping the molten metal.
In the conventional machine, the injection plunger is actuated by a hydraulic cylinder holding the casting sleeve, and while the sleeve is released from stationary mold, the cylinder is tilted, together with the sleeve and the plunger, from a normal vertical position to an inclined position by a tilting device. After the sleeve receives the molten metal at the inclined position, the cylinder is returned together with the sleeve and plunger to the normal vertical position by the tilting device. The tilting device comprises a hydraulic cylinder for actuating a piston rod. The tilting cylinder is pivotally mounted at its end to a stationary base and the piston rod is pivotally mounted to the injection cylinder. In such an arrangement of the tilting device, there is a problem in that the sleeve is forced to stop suddenly at both the normal vertical position and the inclined position and to move rapidly between the two positions. Such motions of the sleeve cause the molten metal in the sleeve to be agitated, and causing the same disadvantageous possibilities as those mentioned above, that is, the scattering and of dropping of the molten metal.